Olefin polymerization with group v metal oxide and alkali metal



United States Patent OLEFIN POLYMERIZAT ION WITH GROUP V lVIETAL OXIDE AND ALKALI METAL Morris Feller, Park Forest, and Edmund Field, Chicago, Ill., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Application February 1, 1954, Serial No. 407,561

19 Claims. (Cl. 260-949) This invention relates to a novel process for the polymerization of ethylene in the presence of alkali metals and subgroup 5 metal oxide catalysts.

One object of our invention is to provide novel and highly useful catalysts and promoters for the preparation of high molecular weight polymers from ethylene-containing gas mixtures. Another object is to provide a novel process for the polymerization of ethylene to high molecular weight normally solid polymers. Still another object of our invention is to provide a novel process for the conversion of gas mixtures comprising essentially ethylene to high molecular weight solid resinous or plastic materials.

A further object is to provide a relatively low temperature, low pressure process for the conversion of ethylene-containing gases to high molecular weight resinous or plastic materials. An additional object of the present invention is to provide a process for the copolymerization of ethylene with other polymerizable materials, particularly with a normally gaseous monoolefin such as propylene, to provide novel resinous materials. These and other objects of our invention will become apparent from the ensuing description thereof.

Briefly, the inventive process comprises the conversion of ethylene principally to high molecular weight normally solid, resinous polymers and to grease-like polymers by contact with an alkali metal (Li, Na, K, Rb or Cs) and vanadia or other subgroup 5 metal oxide, preferably supported on a diflicultly reducible metal oxide such as silica, activated alumina, titania, zirconia, clays, and the like. The inventive process is effected at temperatures between about 75 C. and about 325 C. and pressures between about atmospheric and 15,000 p. s. i. g. or higher, preferably between about 200 and 5000, or about 1000 p. s. i. g. The normally solid materials produced by the catalytic conversion tend to accumulate upon and within the solid catalyst. It is desirable to supply to the reaction zone a liquid medium which serves both as a reaction medium and a solvent for the solid reaction products. Suitable liquid reaction media for polymerization include various hydrocarbons, particularly an aromatic hydrocarbon such as benzene, toluene or xylenes. The conversion of ethylene can be effected in the absence of a liquid reaction medium or solvent and the catalyst containing accumulated solid polymeric conversion products can be treated from time to time, within or outside the conversion zone, to eifect removal of conversion products therefrom and, if necessary, reactivation or regeneration of the catalyst for further use.

The practice of the process of the present invention leads to ethylene polymers of widely variant molecular weight ranges and attendant physical and mechanical properties, dependent upon the selection of operating conditions. The inventive process is characterized by extreme flexibility both as regards operating conditions and as regards the products producible thereby. Thus the present process can be effected over extremely broad ranges of temperature and pressure. The practice of the "ice present process can lead to grease-like ethylene homopolymers having an approximate molecular weight range of 300 to 700, wax-like ethylene homopolymers having an approximate specific viscosity (X 10 between about 1000 and 10,000, and tough, resinous ethylene homopolymers having an approximate specific viscosity (X10 of 10,000 to more than 300,000 [(1 relative -l) l0 By the term tough, resinous polyethylene as used herein we mean polymer having a brittle point below -50 C. (A. S. T. M. method D746-51T), impact strength greater than two foot pounds per inch of notch (A. S. T. M. method D25647T-Izod machine) and minimum elongation at room temperature (25 C.) of 100%.

The process of the present invention may be employed to efiect the copolymerization of ethylene with other polymerizable materials, particularly with propylene, or other mono-olefinic hydrocarbons such as n-butylenes, isobutylene, t-butylethylene; acetylene, butadiene, isoprene, and the like, usually in proportions between about 1 and about 25% by weight, based on the weight of ethylene.

The proportion of sodium or other alkali metal to subgroup 5 metal oxide catalyst (total weight of solid catalyst) may be varied between about 0.05 and about 2.5 parts by weight, but is usually between about 0.5 to about 1 parts by weight per part by weight of the subgroup 5 catalyst. The optimum proportions can be readily determined in specific instances by simple small-scale tests.

The-relative proportion of support to the catalytic metal oxide is not critical and may be varied throughout a relatively wide range such that each component is present in amounts of at least approximately 1 weight percent. The usual metal oxidezsupport ratios are in the range of about 1:20 to 1:1, or approximately 1:10. We may employ conditioned silica-metal oxide catalysts composed of silica base containing about 1 to preferably about 5 to 35%, or approximately 10%, of vanadia or other subgroup 5 catalytic metal oxide supported thereon.

Gamma-alumina or other activated alumina, titania and zirconia may be used as supports for our catalysts. These may be prepared in any known manner and the oxides of vanadium or other subgroup 5 metal may likewise be incorporated in, or deposited on, the base in any known manner. The subgroup 5 metal oxide may be incorporated in the catalyst base in any known manner, e. g. by impregnation, coprecipitation, co-gelling, and/or absorption, and the catalyst base and/or finished catalyst may be heat stabilized in the known manners. Cobalt, calcium, magnesium, copper and zinc salts of vanadic acid may also be employed upon a diflicultly reducible metal oxide support and are preferably treated with hydrogen under conditions to eifect partial reduction thereof before use in our process.

The vanadia or other subgroup 5 metal oxide catalyst is subjected to a reducing or conditioning treatment before use in the polymerization process. The conditioning or reducing treatment is preferably eliected with hydrogen although other reducing agents such as carbon monoxide, mixtures of hydrogen and carbon monoxide (water gas, synthesis gas, etc.), sulfur dioxide, hydrogen sulfide, dehydrogenatable hydrocarbons, etc., may be employed.

Hydrogen can be employed as a reducing agent at tem- 'up'to' 3000 p. s. i. g., or even more. The simplest reducing operation may be effected with hydrogen at about atmospheric pressure.

Reducing gases such as carbon monoxide and sulfur dioxide may be used under substantially the same conditions as hydrogen. Dehydrogenatable hydrocarbons are usually employed at temperatures of at least about 450 C. and not above 850 C. Examples of dehydrogenatable hydrocarbons are acetylene, methane and other normally gaseous parafiin hydrocarbons, normally liquid saturated hydrocarbons, aromatic hydrocarbons such as benzene,- toluene, xylenes and the like, normally solid polymethylenes, polyethylenes or para'fiin waxes,- and the like.

The partial reduction of the metal oxide catalyst in which the metal is present in its pentavalent state can be effected in the presence of the alkali: metal promoter, prior to contacting the combination of catalysts with ethylene.

We have at time observed that an induction period before ethylene polymerization can be eliminatedoi' substantially reduced by pressuring hydro en into-the reactor containing the solvent, ethylene, metal oxide can-- lyst and promoter, e. g. at hydrogen pressures between about 10 and about 900 p. Sri g., preferably 100-400 p. s. i. g. Under these conditions; only a small proportion of the ethylene is' reduced to ethane;

Lithium aluminum hydride, an exceptionally active reducing agent, conditions and activates catalysts eontaining pentavalent subgroup metal oxides even at 'tem peratures as low as 35 (3., although in general, temperatures between about 100 and about 300 C. can be employed. suspension of LiAlI-h in a liquid hydrocarbon at weight ratios of about 0.2 to about 1 LiAlI-Lr to solid catalyst. Sodium hydride (or sodium plus H2) is effective in the reducing and conditioning treatment at temperatures above about 180 C. and may be employed in the same proportions as LiAlH r. Calcium hydride may also be employed to effect some reduction of VzOs supported on gamma-alumina at 230 C. and higher temperatures.

The conditioning treatment hereinabove described is desirable not only for fresh catalyst, but is also required for catalyst which has become relatively inactive in the polymerization step. As will be hereinafter described,

the polymer formed in the polymerization reaction must be continuously or intermittently removed from the catalyst particles, preferably by means of solvents, and it is usually necessary or desirable to condition a catalyst surface which has been thus freed to some extent from polymer before it is again employed for effecting polymerization. When catalyst can no longer be renderedsufiiciently active by simple removal of polymer and conditioning with a reducing gas as hereinabove described, it may be regenerated by extraction with water, am-- monium salts or dilute aqueous acids, thereafterburning combustible deposits therefrom with oxygen followed filter cake, lumps, or shaped pellets. A convenient form in, which the catalyst may be employed is .as granules of about 20100 mesh/inch size range.

The charging stock to the present polymerization prior;-

ess preferably comprises essentially ethylene. The ethylerie charging stocks may contain inert hydrocarbons, as. in refinery gas streams, for example, methane, ethane,

propane, etc. However, it is preferred to employe aspure and concentrated ethylene charging stocks as it is possible, to obtain. When the charging stock containspropylme as well as ethylene, both these olefin s may contributefto the production of resinous high molecular weight prod-.

ucts, The molar ratio of ethylene to propylene maybe,

In practice, the catalyst is treated with a by the conditioning step. Detoxification of the catalysts varied over the range of about 0.1 to about 20. The charging stock may contain other components such as small amounts of hydrogen and it may contain other polymerizable materials such as butylene, acetylene, tbutylethylene, etc.

It is desirable to minimize or avoid the introduction of oxygen, carbon dioxide, water or sulfur compounds into contact with the catalyst. a

In general, polymerization can be effected inthe present process at temperatures between about and about 325 C. Increasing the polymerization temperature tends to reduce the average molecular weight and density of the polymer produced by the process. Usually polymerization is effected in the present process at temperatures of at least about C. or the preferred narrower range of about 225 to about 275 C.- The conjoint use of polymerization temperatures between about 230 and about 260 C. and a liquid hydrocarbon reaction medium such as benzene, Xylenes, decaliri, or methyl decalins is highly desirable in producing ethylene polymers having specific viscosities (x10 ranging on the average from about 10,000 to about 30,000.

It has been found that the present process can be employed for the production of relatively high molecular weight ethylene polymers at relatively low pressures. The process of the present invention may be effected to some extent even at atmospheric pressure. The upper limit of polymerization pressure is dictated by economic considerations and equipment limitations and may be 10,000 p. s. i. g., 20,000 p. s. i. g., or even more. A generally useful and economically desirable polymerization pressure range is between about 200 and about 5000 p. s. i. g., preferably between about 500 and about 1500 p. s. i. g., e. g. about 1000 p. s. i. g.

The contact time or space velocity employed in the polymerization process will be selected with reference to the other process variables, catalysts, the specific type of product desired and the extent of ethylene conversion desired in any given run or pass over the catalyst. In general, this variable is readily adjustable to obtain the desired results. In operations in which the olefin charging stock is caused to flow continuously into and out of contact with the solid catalyst, suitable liquid hourly space velocities are usually selected between about 0.1 and about 10 volumes, preferably about 0.5 to 5 or about 2 volumes of olefin solution in a liquid reaction medium, which is usually an aromatic hydrocarbon such as benzen'e, xyl'enes, or tetralin, or a cycloaliphatic hydrocarbon, such as decalin (decahydronaphthalene).

The amount of ethylene in such solution may be in the range of about 2 to 50% by Weight, preferably about 2 to about 10 weight percent or, for example, about 5 to 10 weight percent. When the ethylene concentration in the liquid reaction medium is decreased below about 2 weight percent, the molecular weight and melt viscosity of the polymericproducts tend to drop sharply. In general, the rate of ethylene polymerization tends to. increase with increasing concentration of the ethylene in the liquid reaction medium. However, the rate of ethylene polymerization to form high molecular weight, normally solid polymers is preferably not such as to yield said solid polyatom in. quantities which substantially exceed the solubility thereof in said liquid reaction medium under the reaction conditions, usually up to about 5-7 weight percent, exclusive of the amounts of polymeric products which are selectively adsorbed by the catalyst. Although ethylene concentrations above 10 weight percent in the liquid reaction medium may be used, solutions of ethylene polymer above 510% in the reaction. medium become very viscous and difiic'ul-tto handle and severe cracking or spalling of the solidmetal oxide catalyst particles or fragmerits may occur, resultingin catalyst carry-over as fines with the solution of polymerization products and extensive loss'of catalyst from 'the reactor.

In batch-operations, operating periods, of between one.-

half and about 60 hours are usually employed and the reaction autoclave is charged with ethylene as the pressure falls as a result of the olefin conversion reaction.

The solvent:catalyst weight ratio can be varied in the range of about to about 3000, or even higher for flow systems. The employment of high solventzcatalyst ratios, which is rendered possible by the presence of an alkali metal, is very important in obtaining substantial yields of polymer.

The olefin charging stocks can be polymerized in the gas phase and in the absence of a liquid reaction medium by contact with the alkali metals and metal oxide catalysts.

Upon completion of the desired polymerization reaction it is then possible to treat the solid catalyst for the recovery of the solid polymerization products, for example by extraction with suitable solvents. However, in the interests of obtaining increased rates of. olefin conversion and of continuously removing solid conversion products from the catalyst, it is much preferred to effect the conversion of the olefin in the presence of a suitable liquid reaction medium. The liquid reaction medium may also be employed as a means of contacting the olefin with catalyst by preparing a solution of the olefin feed stock in the liquid reaction medium and contacting the resultant solution with the polymerization catalyst.

The liquid reaction medium functions as a solvent to remove some of the normally solid product from the catalyst surface.

Various classes of hydrocarbons or their mixtures which are liquid and substantially inert under the polymerization conditions of the present process can be employed. Members of the aromatic hydrocarbon series, particularly the mononuclear aromatic hydrocarbons, viz., benzene, toluene, xylenes, mesitylene and xylene-p-cymene mixtures can be employed. Tetrahydronaphthalene can also be employed. In addition, we may employ such aromatic hydrocarbons as ethy-lbenzene, isopropylbenzene, secbutylbenzene, t-butylbenzene, ethyltoluene, et-hylxylenes, hemimellitene, pseudocumene, prehnitene, isodurene, diethylbenzenes, isoamylbenzene and the like. Suitable aromatic hydrocarbon fractions can be obtained by the selective extraction of aromatic naphthas, from hydroforming operations as distillates or bottoms, from cycle stock fractions of cracking operations, etc.

We may also employ certain alkyl naphthalenes which are liquid under the polymerization reaction conditions, for example, l-methylnaphtha-lene, 2-isopropylnaphthalene, l-n-amylnaphthalene and the like, or commercially produced fractions containing these hydrocarbons.

Certain classes of aliphatic hydrocarbons can also be employed as a liquid hydrocarbon reaction medium in the present process. Thus, we may employ various saturated hydrocarbons (alkanes and cycloalkanes) which are liquid under the polymerization reaction conditions and which do not crack substantial-1y under the reaction conditions. Either pure alkanes or cycloalkanes or commercially available mixtures, freed of catalyst poisons, may be employed. For example, we may employ straight run naphthas or kerosenes containing alk anes and cycloalkanes. Specifically, we may employ liquid or liquefied a'lloanes such as n-pentane, n-hexane, 2,3-dirnethylbutane, n-octane, iso-octane (2,2,4-trimethylpentane), n-decane, n-dodecane, cyclohexane, methylcyclohexane, dimethylcyclopentane, ethylcyclohexane, decalin, methyldecalins, dimethyldecalins and the like.

We may also employ a liquid hydrocarbon reaction medium comprising liquid olefins, e. g., n-hexenes, cyclohexene, octenes, hexadecenes and the like.

The normally solid polymerization products which are retained on the catalyst surface or grease-like ethylene polymers may themselves function to some extent as a liquefied hydrocarbon reaction medium, but it is highly desirable to add a viscosity-reducing hydrocarbon, such as those mentioned above, thereto in the reaction zone.

0 The liquid hydrocarbon reaction medium should be freed of poisons before use in the present invention by acid treatment, e. g., with anhydrous p-toluenesulfonic acid, sulfuric acid, or by equivalent treatments, for example with aluminum halides, or other Friedel-Crafts catalysts, maleic anhydride, calcium, calcium hydride,

sodium or other alkali metals, alkali metal hydrides, lithium aluminum hydride, hydrogen and hydrogenation catalysts (hydrofining), filtration through a column of copper grains or 8th group metal, etc., or by combinations of such treatments.

We have purified C. P. xylenes by refluxing with a mixture of 8 weight percent M0O3-Al203 catalyst and LiAlH4 (50 cc. xylene-1 g. catalyst-0.2 g. LiAlI-Ia.) at atmospheric pressure, followed by distillation of the xylenes. Still more effective purification of solvents can be achieved by heating it to about 225 C.-250 C. with either sodium and hydrogen or NaH plus an 8 weight percent molybdena-alumina in a pressure vessel.

Temperature control during the course of the ethylene conversion process can be readily accomplished owing to the presence in the reaction zone of a large liquid mass having relatively high heat capacity. The liquid hydrocarbon reaction medium can be cooled by heat exchange inside or outside the reaction zone.

When solvents such as xylenes are employed, some alkylation thereof by ethylene can occur under the reaction conditions. The alkylate is removed with grease in the present process, can be separated therefrom by fractional distillation and can, if desired, be returned to the polymerization zone.

The methods of polymerization and equipment described in our application for United States Letters Patent, Serial No. 324,607 may be employed without substantial change in employing the present catalysts and promoters.

The following are non-limitative examples of our invention. The polymerization reactions were carried out in a 250 ml. stainless steel autoclave provided with a magnetically-actuated stirrup-type stirring device which was reciprocated within the reaction zone.

Example 1 The catalyst which was employed was 10 weight percent V205 supported upon silica gel, 30 to mesh per inch, which was prereduced before use with hydrogen at 350 C. and atmospheric pressure for about 16 hours. The reactor was charged under a blanket of hydrogen with l g. of the prereduced catalyst, 0.2 g. of sodium and cc. of dehydrated C. P. benzene- The reactor contents were heated with stirring to 231 C. and ethylene was then pressured into the reaction mixture to an initial partial pressure of 640 p. s. i. Reaction was continued for 44 hours with intermittent repressuring of ethylene into the reactor. The reaction yielded 3.54 g. per g. of the vanadia-silica catalyst of a tough, solid ethylene polymer having a density at 24 C. of 0.9620, Williams plasticity of 17 and melt viscosity of 10 poises (method of Dienes and Klemm, J. Appl. Phys. 17, 45 8 78 (1946)). The reaction also yielded 1.7 g. per g. of catalyst of solid, grease-like polyethylenes.

When the vanadia-silica catalyst was employed without any promoter, no solid ethylene polymer could be obtained, as shown by the following experiment. The autoclave was charged with 10 g. of 10 weight percent V205 supported on silica gel, about 40 to 100 mesh per inch, prereduced with hydrogen at 350 C. and atmospheric pressure for 16 hours. The reactor was also charged with 100 cc. of dehydrated and decarbonated toluene. These operations were performed under a hydrogen blanket. The contents of the reactor were then heated with stirring to 232 C. and ethylene was then introduced to an initial pressure of 775 p. s. i. The reactor contents were stirred for 20.5 hours. This reaction yielded no solid ethylene polymer; only 4 g. of a colored liquid were obtained.

As a further control test, a vanadia+alumina catalyst was employed in-the absence ofa promotcnas shown in the following experiment. Thereactor was-charged with 10g. of10 weightpercentVzOa supported'upon a gammaalumina, prereduced with hydrogen .at 350 -C. in =the same manner-as the aforementioned vanadia-silica catalysts. The reactor was-charged with -.5 cc.-of dehydrated and decarbonated toluene :and the'contents were heated with stirring to 202 C. Ethylene 'wasthen .introduced into the reactor to apartial pressure of 850 -p. -s. i. and stirring was continued for 22 hours. This reaction yielded only a .trace amount of solidethylene polymer.

' Example 2 The reactor was charged with 1g. of the prereduced vanadia-silica catalyst .preparedastin Example 1, 0.2 g. of sodium and 100cc. of decalin which had been purified by treatment with silica .gel. .All charging operations were conductedunder adryhydrogen rgas blanket. The reactor contents were heated with stirring to 230 -C. and ethylene was then introducedinto the reaction mixtureto a partial pressure of 850p. s. i. Reaction was continued for 20.5 hours. This operation yielded 36 weight percent, based-on .the weight of the vanadia-silica catalyst, of tough, solid polyethylenes and 113 weight percent of solid grease-like polyethylenes.

Example '3 Example 4 The process of Example l'is repeated but the sodium is i replaced by .one-tenth'of its weight of potassium. The products are Worked up to separate solid polyethylenes.

Example 5 The reactor was charged with 1 g. of the prereduced vanadia-silica catalyst prepared as in Example 1, 0.3 g. of lithium and 100 cc. of purified toluene. The reactor contents-were heated with stirring to 252 C. and ethylene was then pressured into the reactor to an initial value of 635 p. s. i. Ethylenewas pressured into the reactor from time to time as it was consumed. Reaction was continued for a period of 92 hours, over the course of which the 'ethyleneprcssure drop was 785 p. s. i. The operation yielded 1.7 g. perg. of catalyst of tough, solid polyethylene having a density at 240 C. of 0.9567 and melt viscosity of 1.2 l0 poises. The operation also yielded 9.7 g. per g. of catalyst of solid grease-like polyethylenes and some alkylated toluenes.

' Example 6 The process of Example 1 is repeated but 10 weight percent TazOs supported upon an activated alumina is substituted in equal parts by weightforthe vanadia-silica catalyst of Example 1. The reaction mixture is worked up to separate normally solid polyethylene.

The polymers produced by the process'of this invention canbe subjected to such after-treatment as may be desired, to fit them for particular uses or to impart desired properties. Thus,'the polymers can be extruded, mechanically milled, filmed or cast, or converted .to sponges or latices. Antioxidants, stabilizers, .fillers, extenders, plasticizers, pigments,iinsecticides, fungicides, etc. canbe incorporated in thepolyethylenes and/or in by-product alkylates or greases. The polyethylenes may be employed as coating materials, gas barriers, binders, :etc. to :even a wider extent .than-polyethylenes made .bypriorprocesses.

The polymers produced by .the process of the. present invention, especially the polymers having high'specificyiscosities, can be blended with the lower-molecularweight polyethylenes to impartlstifines's .or'flexibilityor otherdesired properties thereto. The solid.resinousproductsprodueed by the process of the .presentinvention .can,. likewise,'be blended.in any desiredproportions withhydroe carbon oils, waxes,.suchas parafiinor petrolatum waxes,

carbon lubricating oils to increase V. I. and to decrease oil consumption when the-compounded oils are employed in motors; larger amounts of ,polylethylenes may .be com-.

pounded with .oils of various :kinds and for various purposes.

The products having .a molecular :weight .of 50,000.01,

more produced by the present invention, can be employed insmall proportions to substantially increase the viscosity of fluent liquid hydrocarbon oils and as gelling agents for such oils. The solution of about .1 gram .of an ethylene polymer having a specific viscosityX 10 of about 50,000 in about oneliter ofxylenes at a temperature close to the boiling pointproduces an extremely viscous solution. 7

The polymers produced by the present process can be subjected to chemical modifying treatments, such as halogenation, halogenation followed by dehalogenation,.sulfohalogenation by treatment with sulfuryl chloride ormixtures of chlorine andsulfur dioxide, sulfonation, and other reactionsto which'hydrocarbonsmay be subjected.

This application is a ,continuation-in-part of our application forUnitedStates,LettersP-atent, Serial No. 324,610, filed on December .6, 1952,'now U. ,8. Patent 2,691,647.

Having thus described ourinvention, what we claim is:

"1. In a process vfor the productionof a-normally solid polymer, the steps of .contactingethylenewith an alkali metal and acatalyst comprising essentially an oxideof a metal of subgroup 5 of the periodic table at apolymerization reaction temperature betweenabout 75 .C. and about 325 C., and separating a normally solid polymer thus produced.

2. The process of claim 1 wherein the ratio of said alkali metal to said catalyst, by Weight, is between about 0.05 and about 2.5.

3. In a process for the production of a normally solid polymer, the steps of contacting ethylene with an alkali metal and a catalyst prepared by treating a minor proportion of a subgroup 5 metal pentoxide supported upon a major proportion of a difiicultlyreducible metal oxide with a reducing gas at a temperature between about 350 C. and about'850 C. to produce a lower-valent subgroup 5 metal oxide, and separating a normally solid polymer thus produced.

4. The process of claim 3 wherein said reducing gas is hydrogen.

5. The process of claim 3 wherein the ratio of alkali metal to said-catalyst, by weight, is between about 0.05 and about 2.5.

6. The process of claim 3 in which the polymerization I reaction is effected in the hon reaction medium.

7. The process of claim 6 wherein metal pentoxide isVzOs.

8. The process of claim 6 wherein said subgroup 5 metal pentoxide is NbzOs.

9. The process of claim 6 wherein metal pentoxide is Tazos.

10. The process of claim 6 wherein said alkali metal is sodium.

11. The process of claim 6 wherein saidalkali metalis lithium.

l2. Theprocessof claim 'o whereinsaid'alkali metal'is potassium.

presence of a liquid hydrocarsaid subgroup 5 said subgroup 5 13. .-In aprocess fonthe production of a'normallysolid ethylene polymer, the steps which comprise contacting ethylene in a concentration between about 2 and about 10 weight percent in a liquid hydrocarbon; reaction medium at a reaction temperature between about 200 C. and about 300 C. under pressure with an alkali metal and a catalyst prepared by treating a minor proportion of a subgroup 5 metal pentoxide supported upon a major proportion of a difficultly reducible metal oxide with hydrogen under conditions adapted to efiect partial reduction of said subgroup 5 metal pentoxide while supported upon said diificultly reducible metal oxide, said conditions including a temperature between about 350 C. and about 850 C., the weight ratio of said alkali metal to said catalyst being between about 0.05 and about 2.5, and separating a normally solid ethylene polymer thus produced.

14. The process of claim 13 wherein said liquid hydrocarbon reaction medium is a low-boiling monocyclic aromatic hydrocarbon.

15. The process of claim 14 wherein said hydrocarbon is benzene.

16. The process of claim 13 wherein said alkali metal is sodium.

17. The process of claim 13 wherein said alkali metal is lithium.

18. The process of claim 13 wherein said alkali metal is potassium.

19. The process of claim 13 wherein said alkali metal is sodium and said metal pentoxide is V205.

References Cited in the file of this patent UNITED STATES PATENTS 2,487,564 Lay-ng Nov. 8, 1949 2,634,260 Oarnahan Apr. 7, 1953 

1. IN A PROCESS FOR THE PRODUCTION OF A NORMALLY SOLID POLYMER, THE STEPS OF CONTACTING ETHYLENE WITH AN ALKALI METAL AND A CATALYST COMPRISING ESSENTIALLY AN OXIDE OF A METAL OF SUBGROUP 5 OF THE PERIODIC TABLE AT A POLYMERIZATION REACTION TEMPERATURE BETWEEN ABOUT 75* C. AND ABOUT 325* C., AND SEPARATING A NORMALLY SOLID POLYMER THUS PRODUCED. 